This invention generally relates to combustion dynamics, and more particularly, to systems and methods for efficient mixing of fuel and air within a compact space such as the mainstream air flow of a combustor.
Combustion dynamics occur when the inherent unsteadiness of a flame couples with the natural modes of a combustor and establishes a feedback cycle leading to high amplitudes of pressure perturbations and potential significant damage to the corresponding hardware. Combustion dynamics are known to plague gas turbines for power generation, prime-mover, aviation, and marine applications.
Combustion dynamics is a universal issue with and presents one of the biggest challenges faced by gas turbine manufacturers since the introduction of premixed combustion systems. Various techniques have been employed to address combustion dynamics, including without limitation, altering the generation mechanism, varying the combustor dimensions or damping, and control/suppression of the problem by using active/passive devices/methods.
Combustion dynamics has led to catastrophic combustor damage/failure when observed at very high amplitudes. Even when less severe, it restricts the operational envelope of a gas turbine and hinders the best possible performance. Combustion dynamics is still a pervasive problem with existing and installed gas turbines. Further, with stricter emissions regulations and fuel-flexibility, the problems relating to combustion dynamics are expected to get worse.
One significant issue related to combustion dynamics is directed to efficient mixing of fuel and air within a compact space such as the mainstream air (oxidant) flow tube of a combustor. Presently, injection fuel holes are generally cylindrical and oriented to create normal injection jets. One technique for improving mixing of fuel and air within the mainstream air flow of a combustor includes the use of swirler mechanisms. Swirlers are however, complex in terms of both cost and structure. Further, swirlers generally employ moving parts which adversely impacts system reliability. Some known common structures create high losses aerodynamically and can lead to localized flame holding or flashback. To date, dynamics and acoustics issue resolution has focused generally on active modulation of the fuel injection, rather than passive techniques.
In view of the foregoing, there is a need for a system and method for passively and efficiently mixing of fuel and air within a compact space such as the mainstream air (oxidant) flow of a combustor to achieve optimal operational performance in terms of acoustics, emissions and power output. The system should be simple in terms of structure when compared to known structures for improving mixing of fuel and air with the compact space.